• well when something orbits the sun it spins, the force of the spin forces it into that shape. don;t ask me about the magnetic fields because i don;t know how to explain it lol
• It's to do with gravity. Small objects like meteors are not very round, whereas as large objects like the ones you mentioned are. Larger, heavier, denser objects exhibit enough gravitational pull to cause the object itself to become round, as everything is being pulled into the centre, and a sphere is the best shape to get everything as close to the middle as possible. Everything that has mass exherts a gravitational pull put only large objects have sufficient to cause themselves to become round.
• &quot;If one weren't, it would collapse to a sphere under its own gravity. All the matter tries to fall toward the center, and will if there's nothing in its way. The sphere is the shape in which everything has fallen toward the center as far as it can. Actually, planets bulge out a little at their equators, because of their rotation. So they're not exactly spherical, but pretty close." http://www.newton.dep.anl.gov/askasci/phy99/phy99524.htm
• They are only roughly spherical. The Earth bulges at the Equator for example. The moons of Mars are not spherical at all. But broadly yes large planets are spherical-ish. It is to do with gravity. All the mass is pulled towards the centre equally, since the attraction is universal and applies to all the components of the planet. Hence the sphere is the best option. consider if they were cuboid. The corners would be further from the centre which would indicate they were being attracted less strongly to the centre than the edges (from pythagoras theorem the hypotenuse is longer than the side). Since gravity is universal this doesn't happen.
• planets are obliptical in shape have made obliptical orbits around the sun collecting particals from trillions of revolutions round the sun changing its orbit from time to time, for example the earth and the moon are made of the same matter and are the same relative shape. look up genesis and the solar system. the same question could be asked about gravity and there is no scientific answer to it we no gravity exists but scientists cannott figure out how it works no one knows for sure.
• Planets are round because their gravitational field acts as though it originates from the center of the body and pulls everything toward it. With its large body and internal heating from radioactive elements, a planet behaves like a fluid, and over long periods of time succumbs to the gravitational pull from its center of gravity. The only way to get all the mass as close to planet's center of gravity as possible is to form a sphere. The technical name for this process is "isostatic adjustment." With much smaller bodies, such as the 20-kilometer asteroids we have seen in recent spacecraft images, the gravitational pull is too weak to overcome the asteroid's mechanical strength. As a result, these bodies do not form spheres. Rather they maintain irregular, fragmentary shapes. From: http://ideaplace.org/Why/RoundPlanet.html
• 8-9-2017 Things in space are not round, they are clumped. You have not asked a straight question, so here is an off topic answer: https://possiblywrong.wordpress.com/2011/09/09/if-the-earth-were-a-cube/